Anti-sway device



A il 2, 1963 e. H. CRITTENDEN ETAL 3,375,938

ANT-I-SWAY DEVICE Filed July 11, 1966 5 Sheets-Sheet 1.

ARTHUR E MILLS A T TOR/V5) April 2, 1968 G. H. CRITTENDEN ETAL 3,375,933

ANTI-SWAY DEVICE Filed July 11, 1966 3 Sheets-$heet 5 I uvvLwrms GEOFFREY H. GR/TTE/VDE/V ARTHUR E. MILLS W(QM ATTORNEY United States Patent 3,375,938 ANTl-SWAY DEVICE Geoffrey H. Crittenden, Alameda, and Arthur E. Mills, Orinda, Calif., assignors to Pacific Coast Engineering Company, a corporation of California Filed July 11, 1966, Ser. No. 564,257 13 Claims. (Cl. 212-13) ABSTRACT OF THE DISCLOSURE An apparatus for abating the pendulum motion of large suspended loads. Wire ropes reelable from drums secured to the lifting apparatus, and having a common brake, are secured to the suspended load. A differential assembly permits the wire ropes to unreel without resistance when all are unreeled equally, but applies the brake automatically to any of the ropes which unreel faster than other of the ropes. Spring motors rereel the ropes when they go slack.

BACKGROUND OF THE INVENTION Field of the invention The present invention relates to an anti-sway device and more particularly to an anti-sway device which arrests pendulum motion of a suspended load.

A problem usually encountered in the handling of cargo by cranes is sway of the load and it occurs, because, in most cases, the cargo must be moved with horizontal motion while suspended by cables. Due to this movement, the cargo usually experiences pendulum motion from the horizontal acceleration and deceleration forces inherent to the movement. To accurately position the suspended load for set down and release, it is necessary to wait until the pendulum motion has subsided. Thus, in each cargo handling cycle of the crane, considerable time is lost. To increase the handling capacity of the crane, it is of primary consideration to reduce the time necessary for pendulum motion abatement.

Description of the prior art Many anti-sway devices have been developed for preventing or arresting pendulum motion. One of the most common is a spring loaded tagline cable reel and is most often found in conjunction with clamshell buckets. The main defect with a tagline is that they only act in one direction, and, on the return swing, they pull on the load adding to the force of gravity tending to accelerate the load.

None of the known anti-sway devices prevent sway in more than one direction, while most of them add signif icantly to the forces tending to accelerate the load on the return swing.

The present invention is an anti-sway device designed primarily for use on container cranes to reduce the swaying of swinging of elongated containers when suspended by cables. However, it will be apparent, and it will be pointed out in detail, that the present invention can be utilized for any type of suspended load.

When loading cargo containers on board ship, the containers must be accurately located over the hatch, or cell division of a hatch, so that the containers will be properly aligned in the cell guides. Swaying of the load causes delay because the operator must wait until the load stops swinging before he can accurately spot the setting or cell entrance position for the container.

A comparable situation occurs in the loading or unloading of cargo containers onto truck trailers and/or the loading of the truck trailers and containers onto railroad flatcars for rail transport. In these situations, it is necessary to either locate the container with respect to the trailer or to locate the wheels of the trailer with respect to the pockets or fixed positions of location on the railroad car. As with the handling of the cargo containers for loading into ships, swaying or swinging of the container or trailer delays the loading operation. This is generally more prevalent in the case of inexperienced or less skilled operators.

Summary of the invention The present invention is an anti-sway device which is designed to arrest the swaying motion of a suspended load and to reduce the time necessary for the swinging load to come to a stationary position.

In brief, the present invention is an anti-sway device for arresting pendulum motion of a suspended load relative to its lifting platform. The anti-sway device comprises a pair of rope drums secured to the lifting platform and has ropes reelable therefrom which are secured to the suspended load. A brake means is engaged with the drums for causing work to be done on the bra-ke'means when rope is pulled off of one of the drums independent of the other drum due to the sway of the load but not when the ropes are pulled off of the drums equally.

The invention also contemplates a method for abating pendulum motion of a suspended load and comprises transmitting an arresting force to a first direction of pendulum motion of a suspended load by means of a rope secured by one of its ends to the load and reelable from a drum at the other, causing work to be done as a result of the rope being reeled from the drum due to the motion of the load by means of a. brake interconnected with the drum, disengaging the brake from the drum when the load reverses its direction of swing, and reeling in the rope as it goes slack during pendulum motion of the load in a second direction.

OBJECTS OF THE INVENTION Therefore it is an object of the present invention to provide an anti-sway device for arresting pendulum motion of a suspended load which operates automatically and does not require any control or attention by the crane operator.

It is another object of the present invention to provide an anti-sway device for arresting pendulum motion of a suspended load which does not require any power from an outside source and is a continuously operating self-powered mechanism.

It is a further object of the present invention to provide an anti-sway device for arresting pendulum motion of a suspended load which permits greater acceleration and decleration rates during horizontal movement and faster rates of travel when moving the load than have heretofore been possible.

It is yet another object of the present invention to provide an anti-sway device for arresting pendulum motion of a suspended load which is easily adjustable to control the sway of any weight of suspended load.

It is still a further object of the present invention to provide an anti-sway device for arresting pendulum motion of a suspended load which automatically adjusts to, and continually operates during, the raising and lowering of the load.

It is still a further object of the present invention to provide a new method of arresting pendulum motion of a suspended load.

sidered in conjunction with the accompanying drawings of which:

FIGURE 1 is a perspective View of the invention installed on a typical crane;

FIGURE 2 is the end elevation of the arrangement of the device illustrating the reeving of the wire ropes of the anti-sway device;

FIGURE 3 is a side elevation of the lifting platform showing one of the parallel shafts, wire rope drums, and the associated parts;

FIGURE 4 is a plan view of the top of the lifting trolley showing arrangement of the elements of the invention;

FIGURE 5 is a side elevation in section of the differential assembly of the present invention;

FIGURE 6 is an end elevation in section of the brake means.

DESCRIPTION OF THE PREFERRED EMBODIMENT Reference is made to the drawings for a description of the invention. The perspective view shown by FIG- URE 1 shows a movable trolley 11 which is supported on top of a self-propelled crane 13. A cargo container lifting spreader 15 is suspended below the movable trolley 11 for picking up cargo containers 17 and/ or truck trailers. The reeving which suspends the lifting spreader 15 and carries the load has substantially vertically depending ropes 19. When the load is lifted and moved in a horizontal direction, the acceleration and deceleration forces of the movement induce pendulum motion in the reeving which causes the load to experience sway.

The wire ropes 21, which are part of the anti-sway device, have no effect on the lifting or lowering of the load. The ropes are reeved from the anti-sway mechanism to the opposite edges of the lifting spreader (FIGURE 2) and their lower ends 23 are secured permanently to the lifting spreader frame 15.

The anti-sway device includes a pair of longitudinal parallel shafts 25 (FIGURE 3) which are rotatably supported by bearing mounts 27 from the frame of the trolley 11 which is the lifting platform. The shafts 25 are suspended along each side beam 29, 31 of the trolley frame and are disposed longitudinal of the trolley (FIG- URE 4). The shafts 25 are divided into three interconnected sections and include a central section 33 and two end sections 35, 37 (FIGURE 3). A wire rope drum 39 is mounted on each of the parallel shaft end sections and each has wire ropes 21 reelable therefrom. One end of the rope or line is clamped to the drum 39 and the other end 23 is attached to the lifting spreader of the suspended load. The ropes are secured to the opposite edges of the spreader to provide a better angle of effect whereby a greater horizontal force component is transmitted for a particular loading of the wire rope.

Wire rope drum rewind means 41 are anchored to the bottom of the trolley frame 11 and engage the parallel shaft end sections 35, 37. The rewind means keeps a continuous torque applied to the end sections of the parallel shafts to wind the ropes on the drums and take up slack in the ropes. Generally, the rewind means are powered by prewound spring means or spring motors.

The spring motors are set or pretensioned one or more turns when the lifting spreader is in the uppermost position of lift. Any lowering thereafter will further wind or load the spring motors to insure positive return or reeling in of the ropes on the drums during subsequent spreader raising or sway arresting operations.

For sets of ropes 21, drums 39, and rewind means 41 are used. The arrangement of a rewind means, a rope, and a drum is called a tagline. The taglines are arranged for operation in the present invention as described and illustrated by the drawings (FIGURES 1, 2, 3). These taglines are used solely by themselves in many instances as an anti-sway device, but they are inadequate except for light service because the spring is usually too weak to be 4 effective or is so strong that it accelerates the load too much on the return swing.

The action of a tagline on the drum under a swaying or oscillating condition of the load is to alternately pull rope off the drum as the load swings away from the drum and to reel in the slack rope on the return oscillation as the load swings back toward the drum.

Unidirectional drive clutches 43 (FIGURE 3) inter connect the parallel shaft central sections 33 to the end sections 35, 37.- The effect is to permit the end sections of the shafts to free-wheel relative to the central sections When the drums 39 are reeling in the rope 21 and, conversely, to cause the central sections to rotate with the end sections when the ropes are unreeled from the drums. The unidirectional drive clutches 43 are sometimes called sprag type couplings which in principle act like a pawl and ratchet wheel drive; they will receive and transmit torque when rotated in one direction and will overrun or spin freely when rotated in the opposite direction Without transmitting torque. The sprag type coupling differs from the ratchet and pawl type in that it will lock in any position whereas the ratchet and pawl type coupling will only lock when engaging a ratchet wheel tooth and the number of engagement positions is limited to correspond to the number of teeth. Either type of coupling will serve the purpose, but the sprag type of device is much more desirable as it effects a much smoother operation in transferring the sway-arresting forces when the swinging load reverses its direction of motion.

A differential assembly 45 having a rotatable casing 47 is supported by the trolley frame 11 between the parallel shafts 25 (FIGURE 2). The casing 47 is suspended below the trolley in bearing mounts 49 (FIGURE 5) which permit the whole assembly to rotate. The external surface of the central cylindrical section 51 of the casing is machined to form a brake drum for a band brake to clamp around.

A pair of opposed pinion bevel gears 53 are rotatably supported on the internal surface 55 of the assembly casing. The pinion gears are secured to the casing on inwardly projecting stub shafts 57 and are disposed 180 from each other in opposed relation on opposite sides of the internal wall 55. Lubricating oil fills the space 58 between the casing 47 and the internal wall 55.

A pair of aligned axle shafts 59 having bevel side gears 61, 63 at their adjacent ends are meshed with the opposed pinion gears 53 inside the differential casing 47. Rotation of a side gear 61 will cause rotation of the pinion gears about their own axes. If the opposite side gear 63 is held stationary, or fixed, the rotation of the first side gear 61 will cause rotation of the pinion gears 53 about their own axes, and, concurrently, translation of the pinion gears in a plane 90 to the axle shafts 59. Translation in this sense is defined as motion of the pinion gears 53 in a circular path around the main axis of the differential gear unit, which is coaxial the axle shafts 59, as distinct from, and in addition to, rotation about its own axis. It is simply planetary gear motion. Since the pinion gears 53 are supported on stub shafts 57 projecting from the internal wall 55 of the differential or gear casing 47, the translation of the pinion gears 53 will cause the differential casing 47 to rotate also. This is possible since the gear case is suspended in the bearing mounts 49 projecting from the trolley frame 11. If the two axle shafts 59 rotate in opposite directions the pinion gears will simply rotate in place on their own axes and have zero translational motion. Hence the differential action.

A pair of drive shafts 65 are aligned with the axle shafts 59 of the differential assembly 45 and are interconnected to the axle shafts 59 through reverse-locking drive couplings 67 whereby the drive shafts 65 can rotate the axle shafts 59 but the axle shafts are locked against rotation when the drive shafts are not rotating. In other words, these reverse-locking drive couplings permit the drive shafts 65 to freely turn the axle shafts 59 but pre-- vent torque feedback from the axle shafts to the drive shafts. They are simply one-way torque transmitting devices. As installed in the present invention, the reverselocking drive couplings 67 provide a positive drive coupling between the drive shafts 65 and the axle shafts 59 which will cause rotation of the side gears 61, 63 thereby driving the pinion gears 53, but, conversely, torque exerted on the side gears and axle shafts by the pinion gears cannot drive back through the reverselocking drive couplings 67 to rotate the drive shafts 65- A chain and sprocket drive means 69 interconnects the two parallel shaft central sections with the two drive shafts of the differential assembly independently. In other words, the parallel shaft central sections 33 have sprockets 71 which are interconnected with sprockets 73 on the drive shafts 65 of the differential assembly by chain drives 75 (FIGURE 2), independent of each other.

Other means of interconnecting the differential assembly 45 with the two parallel shafts 25 can easily be envisioned by one skilled in the art. One of the most apparent means would be to dispose the differential assembly 45 transverse to the parallel shafts 2'5 and drive it directly by bevel gears mounted at the ends of the drive shafts 65 and on the parallel shaft central sections 33. However, the embodiment here described best fits the needs of its particular environment.

A spring-loaded band brake means 77 is secured to the trolley frame for arresting rotation of the differential assembly casing 47. The brake 79 acts on the cylindrical external machined surface 51 of the central section of the casing. The tension of the spring 81 on the brake can easily be adjusted to vary the rate of the anti-sway arresting forces or to adjust the brake to arrest at equal nates different weights of loads. In efiect, the brake is common to all of the rope drums which means that all of the drums are interconnected to the same brake means.

Consideration is now directed to the operation of the anti-sway device. The first condition to be considered is thatof truly vertical lowering of the load without sway. The action on the machine is as follows: both sets of taglines 21 on the parallel shafts 25 pay out from the drums 39 and lengthen at the same rate of unreeling. As the taglines lengthen, the drums are caused to rotate. Since the rotation is in a direction to unreel the taglines, all of the unidirectional sprag clutches 43 engage and drive the corresponding parallel shaft central sections 33 and the respective chains 75 and sprockets 7'1, 73. This causes the drive shafts 65 to rotate, which rotation is transmitted through the reverse-locking drive couplings 67 to turn the axle shafts 59 and their side gears 61, 63.

The taglines 21 are wound on their drums 39 in the same direction on each of the parallel shafts 25, but in opposite directions from the taglines on the drums of the other parallel shaft so that the drums and shafts and all corresponding machinery on opposite sides of the differential assembly unit 45 rotate in opposite directions. Hence, the differential side gears 61, 6'3 rotate in opposite directions also, so that the pinion gears rotate in place without turning the casing or doing work on the brake while the lifting spreader is being lowered.

It is a necessary requirement that all of the drums 39 be of the same diameter and that they be equally spaced outward from the center of rest which is the center line of lifting that extends in a vertical plane. Likewise the tagline connection 23 to the load, or the lifting spreader 15, must be evenly or equidistantly spaced from the center of rest. Provided these conditions are met within the practical limits of machinery manufacture, then the speed of tagline pull and differential side gears 61, 63 rotation during vertical lowering will be the same but in opposite directions. Under these conditions of equal angular rotation in opposite directions, the pinion gears 53 will rotate about their own axes but they will not experience translation. Therefore, the differential casing 47 does not rotate and work is not done on the brake. Throughout the lower-ing cycle the spring motors 41 are further tensioned by the unreeling of the taglines 21.

Pendulum motion arresting forces are transmitted to the suspended loads only when work is on the brake. In the case of truly vertical lowering without sway, there is no rotation of the differential casing so that no work is done on the brake. Thus, there are no arresting forces imposed on the taglines other than the increasing rewind forces during the normal lowering cycle.

If vertical raising of the load is effected without side sway, the taglines are retrieved or reeled onto the drums 39 by the rewind means 41 at an equal rate of speed and the unidirectional drive couplings 43 simply over-run. Only the end sections 35, 37 of the parallel shafts rotate during vertical raising so that the parallel shaft central sections 33 and all the other machinery is stationary and no work is done by the brake.

Consideration is next given to the case or condition of sway induced by stopping the trolley during horizontal travel. In the case of large cargo containers, the trolley and lifting platforms are relatively light compared to the weight of the lifting beam and suspended load. The brakes of the trolley are good and hence it has good stopping ability. If the power is cut, the trolley will stop suddenly, but the suspended load will swing on in a radial path until all the kinetic energy or inertia is converted into potential energy, or more simply, until it reaches its highest position of swing commensurate with its speed and Weight. Overlooking friction, 'Which is relatively small, the only restraining or retarding force in the system, without an anti-sway device, is a horizontal component of the gravitational force acting on the load. This force will vary from nothing at the horizontal tangential point and will increase as a function of the tangent of the angle of swing and the suspended weight.

When the anti-sway device is included, a further restraining force is added to the horizontal retarding moment. As the load swings, two of the four taglines 21 will be lengthened in the direction of swing. Additional wire rope is thereby pulled off the drums 39 thus causing the two drums and the parallel shaft end sections 35, 37 to rotate. As previously explained, the unidirectional drive or sprag couplings 43 are installed so that rotation due to lengthening of the taglines will cause rotation of the parallel shaft central section 33 adjacent the two end sections on which the drums are located. A torque is therefore applied to the shaft 25 and is equal to the tagline pull multiplied by the drum radius. This torque is thereby transmitted from the end sections of the shaft through the unidirectional sp-rag couplings to the central section and thereby further transmitted through the chain and sprocket drive means 69 to the centrally disposed differential assembly gear unit 45 by means of the input drive shaft 6'5. (The torque is varied according to the ratio of the chain drive sprocketsrln a preferred embodiment the ratio of a drive is reduced by ten to three.) The torque is transmitted from the drive shaft through the reverselocking drive coupling 67 to the axle shaft 59 whereby it rotates the side gears 61, 63.

Concurrently, the rope drums 39 on the other parallel shaft 25 are rewinding the rope 21 coming slack as the suspended load moves toward the shaft. The unidirectional drive clutches 43 are over-running permitting the parallel shaft central sections 33 to remain at rest with the chain drive and the respective drive shaft of the differential assembly. Since the drive shaft is at rest, the adjacent axle shaft and its side gear are held locked against rotation in either direction by the reverse-locking drive coupling. Thus, one side gear rotates the pinion gears against the other locked side gear causing the pinion gears to translate and causing the differential casing to rotate. Hence, unreeling of the tagline causes translation of the pinion gears 63 and rotation of the differential housing 47. Rotation of the differential case causes work to be done on the brake drum and provides the corrective tagline resistance to unreeling which arrests the pendulum motion of the suspended load.

The pendulum motion of sway continues until the load reaches the apex of its swing at which point it comes to a momentary stop and rotation of all the drums ceases. The direction of pendulum motion then reverses and begins to swing back. The action of the components of the anty-sway device is then completely reversed. The taglines which were providing the arresting force to the load go slack as the load swings back and their drums retrieve or reel in the tagline by virtue of the spring motors. The opposite pair of taglines are pulled off of the drums causing them to rotate the differential assembly casing against the brake as described with respect to the first direction of sway.

The invention operates to provide a restraining or arresting force to the pendulum motion of a suspended load in both directions of swing and will continue to arrest the oscillation until the load is fully abated by the action of the braking friction and the restraining tagline pull. This two-way correctional restraint of sway is a basic and important feature of the present invention. The tagline pull or force is a direct function of, and in proportion to, the brake torque setting which in turn is a function of the brake radius spring force exerted on the brake shoes, the coefficient of friction of the brake linings, and the geometry of the brake. All of these may be varied as required to meet the needs of a particular installation or the sway-stopping time desired. With modifications evident to one skilled in the art, other brake systems such as disc brakes or eddy current electrical brakes could be substituted into the invention.

It will be seen that for pendulum motion, as induced during starting or stopping of horizontal motion, or by any other means, the invention will operate freely to apply a restraining or arresting force to prevent sway in both directions of motion. However, during the operation of truly vertical raising or lowering, no restraining forces (as distinct from rope rewind forces) are applied to the taglines.

A full consideration of the various types of motion which might occur must include the case of a load which is unevenly positioned in a cargo container. If, for instance, the center of gravity is closer to one end of a cargo container than the other, and the container, while it is moving horizontally while disposed crosswise to the direction of motion, is suddenly stopped, it would appear that one end, the heavier end, would swing in a greater are than the lighter end due to its greater momentum. However, since the taglines are geared together, they will feed out equally. Hence the swinging arcs will be equal and the resulting swing due to an unevenly balanced container will not result in a rotational pendulum motion about some point on the container. The device of the present invention in addition to quickly arresting a swinging unbalanced load, will arrest it in a smooth and even manner.

The full concept of the present invention includes a new and novel method for arresting pendulum motion of an elongated suspended load which occurs in the process of transporting it. The method comprises; securing a pair of taglines from each of two parallel shafts to opposite sides of the load as line is pulled from one of the shafts, driving a rotatable differential assembly which is interconnected with the shafts to rotate when taglines are reeled off of one of the shafts independent of the other, but not when the taglines are pulled off the shafts at an equal rate of speed, and reeling in the taglines on the other of the shafts, doing work on a brake means engaged with differential assembly when the assembly rotates, and reversing the action when the suspended load reverses direction.

It will be evident to those skilled in the art that an anti-sway device utilizing only two taglines can be arranged whereby the effect of the invention is utilized but some of the described elements of the preferred embodiment are not. This would be particularly suitable where the load is supported by single point suspension and is not elongated like a cargo container. This could be done by having a single tagline extending to the load from one side of the center of rest and a second drum on the other side of the point of suspension generally opposed to the first drum for providing the counteracting arresting force. The drums would include a rewind means for retrieving the slack taglines and would be connected to the differential assembly by means such as chains and sprockets or by simply turning the assembly crosswise between the two drums and driving it directly by gears.

A further arrangement utilizing the present invention would involve two sets of single drums disposed at to each other and two differential assemblies whereby they would abate all pendulum motion by providing at 360 arresting effect. Likewise, two complete systems similar to the described embodiment of the invention could be disposed crosswise to each other to abate any type of pendulum motion.

The present invention has many advantages due to the variable brake torque settings which can be selected by simply loosening or tightening the band brake. The device can be used to completely eliminate sway by setting the band brake to lock the differential unit. Since side sway or pendulum motion is induced in the load by the forces of acceleration and deceleration, if the rate of acceleration or deceleration is such that the force of acceleration is less than the horizontal arresting force component of the tagline pull, which force is a function of the brake setting, then the tagline will prevent sway completely. Relaxation of the braking torque will of course reduce the tagline tension and permit the anti-sway device to operate as designed and will effect a dampening or arresting action on sway of the load in both directions of movement.

A most important advantage of the present invention is that the operation of the device is entirely automatic. There are no manual controls and the device does not require any attention by the crane operator. It does not require any power from an outside source and is completely self-contained.

This anti-sway device has proved to be extremely efficient in arresting or preventing sway and pendulum motion of suspended loads. It permits a crane to move at higher speeds while carrying loads and the crane trolley to move loads crosswise to the crane much faster. This increases the loading and unloading speed for cargo handling, thereby increasing the capacity and efficiency of operation.

It will be apparent from the foregoing description of the invention in its preferred form that it will fulfill all the objects attributable thereto, and while it is illustrated and described in detail, the invention is not to be limited to such details as have been set forth except as may be necessitated by the appended claims.

We claim:

1. An anti-sway device for arresting pendulum motion of a suspended load relative to its lifting platform, said anti-sway device comprising:

at least one pair of rope drums secured to said platform on opposite sides of the center of rest of said load and having ropes reelable therefrom, said ropes being secured to opposite sides of said load,

rewind means engaged with said drums for taking up slack in said ropes, and

brake means engaged with both of said drums for causing work to be done on said brake means by the rope which is pulled off of one of said drums faster than the other rope is pulled off of the other drum due to the sway of said load, but not when said ropes are pulled off of said drums equally.

2. The anti-sway device of claim 1 wherein said brake means includes a brake drum rotatably supported by said platform,

a brake shoe secured to said platform, and

clutch and differential means for driving the brake drum of said brake assembly against said brake shoe when the rope is pulled off of one of the drums faster than theother rope is pulled off of the other of said drums, but not when the ropes are pulled off of both of the drums equally, said clutch means overrunning when the ropes are rewound on the rope drums.

3. The anti-sway device of claim 2 including reverse locking drivemeans for permitting work to be done on said brake drum when said ropes are pulled from one of the drums faster than the ropes are pulled off of the other of said drums but preventing reverse rotation from being transmitted from said brake assembly to the latter of said drums.

4. The anti-sway device of means further includes a differential assembly having a rotatable casing supported by said platform between said parallel shafts and forming a brake drum, said assembly including a pair of opposed bevel pinion gears rotatably sup ported on the internal surface of said casing,

a pair of aligned axle shafts having bevel side gears at their adjacent ends meshed with said opposed pinion gears,

a pair of aligned axle shafts having bevel side gears at their adjacent ends meshed with said opposed pinion gears,

a pair of drive shafts interconnected to said axle shafts through reverse-locking drive couplings whereby said drive shafts can drive said axle shafts but said axle shafts are locked against reverse rotation when said drive shafts are not rotating,

drive means independently interconnecting said drums with said drive shafts through said clutch means.

5. An anti-sway device for arresting pendulum motion of an elongated load relative to its lifting platform, said anti-sway device comprising:

at least four rope drums supported by said platform on interconnected shafts and having ropes reelable therefrom and secured to said load, said drums being arranged to operate in pairs with the two drums in each pair disposed on the same side of the center of rest of the suspended load and Operating synchronously for arresting pendulum motion of the load in one direction of sway,

brake means engaged with and common to all of said drums for causing work to be done on said brake means by the rope which is pulled off of one of the pairs of drums faster than the other rope is pulled off of the other pair of drums due to the sway of the load, but not when said ropes are pulled off of said drums equally, and

rope rewind means engaged with said drums for taking up slack in said ropes.

claim 2 wherein said brake 6. The anti-sway device of claim 5 wherein said drums are arranged on two parallel shafts disposed on opposite sides of the center of rest of said load with one pair of drums on one shaft and the other pair of drums on the other.

7. The anti-sway device of claim 6 wherein said brake means includes a brake drum rotatably supported by said platform,

a brake shoe secured to said platform, and

clutch and differential means for driving the brake drum of said brake assembly against said brake shoe when the ropes are pulled off of one of the drums on one of said parallel shafts faster than the other ropes are pulled off of the other of said shafts, but not when the ropes are pulled off of the drums on both of said shafts equally, said clutch means overrunning when the ropes are rewound on the rope drums.

8. The anti-sway device of claim 7 including reverse locking drive means for permitting work to be done on said brake means when said ropes are pulled from the drums on one of said shafts, but preventing reverse rotation from being transmitted from said brake assembly to the other of said parallel shafts.

9. The anti-sway device of claim 7 wherein said brake means futrher includes a differential assembly having a rotatable casing supported by said platform between said parallel shafts and forming said brake drum, said assembly including a pair of opposed bevel pinion gears rotatably supported on the internal surface of said casing,

a pair of aligned axle shafts having bevel side gears at their adjacent ends meshed with said opposed pinion gears,

a pair of drive shafts interconnected to said axle shafts through reverse-locking drive couplings whereby said drive shafts can drive said axle shafts but said axle shafts are locked against reverse rotation when said drive shafts are not rotating,

drive means independently interconnecting said parallel shafts with said drive shafts through said clutch means.

10. The anti-sway device of claim 6 wherein said shafts include clutch means to permit said drums to individually disengage from said brake means and rotate freely when rewinding said ropes.

11. An anti-sway device for arresting pendulum motion of a suspended load relative to a lifting platform, said anti-sway device comprising:

a pair of parallel shafts rotatably supported by and below said platform, said shafts being divided into three interconnected sections including a central and two end sections,

wire rope drums mounted on each of said parallel shaft end sections and having wire ropes reelable therefrom, said wire ropes secured to an opposite edge of said suspended load,

prewound spring means anchored to said platform and engaging said parallel shaft end sections for tensioning said drums to take up slack in said ropes, said spring means being further wound for re-reeling by the action of said ropes unreeling from said drums,

unidirectional drive clutches interconnecting said parallel shaft central sections to said end sections permitting said end sections to free-Wheel relative to said central sections when said drums are reeling in said rope but causing said central sections to rotate with said end sections when said ropes are unreeled from said drums,

a differential assembly having a rotatable casing supported by said platform between said. parallel shafts, said assembly including a pair of opposed bevel pinion gears rotatably supported on the internal surface of said casing,

a pair of aligned axle shafts having bevel side gears at their adjacent ends meshed with said opposed pinion gears,

a pair of drive shafts aligned with said axle shafts and interconnected to said axle shafts through reverselocking drive couplings whereby said drive shafts can drive said axle shafts but said axle shafts are locked against reverse rotation when said drive shafts are not rotating,

drive means interconnecting said parallel shaft central sections with said drive shafts independently, and

spring loaded hand brake means secured to said platform for arresting rotation of said differential assembly casing.

12. A method for abating pendulum motion of a load suspended from a platform comprising:

transmitting arresting forces to the suspended load for counteracting the pendulum motion thereof by means of at least two ropes secured to said load and reelable from individual drums secured to said platform, one of said ropes transmitting an arresting force to said load when it swings in one direction, and the other of said ropes transmitting an arresting force 1 1 to the suspended load when it swings in a reverse direction,

causing Work to be done on a brake means common to said drums when rope is reeled from one of said drums faster than off of the other of said drums but not when rope is reeled from said drums at an equal rate of speed, and

rewinding the ropes on said drums when said ropes go slack.

13. In the process of transporting an elongated suspended load, the method of arresting pendulum motion comprising:

securing a pair of taglines to opposite sides of the load from each of two parallel shafts disposed on opposite sides of the center of rest of said load,

as line is pulled from one of the shafts due to sway of the load, driving a rotatable differential assembly which is interconnected with said shafts for rotation when taglines are reeled oil? of one of said shafts independent of the other, but not when the taglines are pulled off the shafts at an equal rate of speed,

and reeling in the taglines on the other of said shafts, doing work on a brake means engaged with said diiferential assembly when said assembly rotates, and reversing the action when the suspended load reverses direction of sway.

References Cited UNITED STATES PATENTS 2,627,984 2/1953 Senn et al 2l258 2,805,781 9/1957 Senn et al. 21258 3,081,884 3/1963 Minty 212126 3,107,791 10/1963 Michael 21258 3,179,259 4/1965 McLean 212l1 ANDRES H. NIELSEN, Primary Examiner. 

